Thanks. The layout from the top down is grill, existing 200mm case fan, metal plate, sunken (toward the inside of the case, I see) mounting holes, then my rad (I guess), then fans on the inside side of the rad if I want to use them. I think I see now that my sequence must be, remove grill, remove 200mm fans, use short screws to mount the rad (the screw heads must not rise above the sunken mount dimples, then remount the top fans, remount the grill. The top fans look like they pull air through the rad and out of the case. Wow, I will be impressed if all these things line up (and will report back here, of course).

Do I need to worry about sealing the gaps between the rad edges and the mounting plate, and the gap between the mounting plate and the fans? (I think the fans already fit pretty close to the mounting plate). In other words, should I worry about the fans sucking air in between the fan and the rad when the fans are 200m and the rad is 120mm? If the air resistance through the rad is not high (and its not supposed to be, I think, for low flow rads), then a small rad-plate-fan gap won't be a big thing, right?